Is grain spawn to blame if I have problems with oyster mushrooms?

Many mushroom growers believe that the quality of oyster mushroom mycelium can be compared in this way: inoculate spawn from two different companies into the same substrate.

It is assumed that if the substrate is of the same quality, and one of the strains overgrows poorly or has a lower yield, this means that this particular spawn is of lower quality.

I don’t know if there is such a misconception in your country, but such a comparison is not correct.

Can different strains be compared?

Your substrate may not be of ideal quality, which will result in differences in germination between different strains from different suppliers.
Some of the strains may be more aggressive in capturing the substrate, but after growth, do not give primordium for a long time.
Or your microclimate will be suitable for one strain, but unfavorable for another. For example, winter strains may produce lower yields at a temperature of +15 than universal ones, since their optimum temperature is +8...+10.
Or one strain needs 90% humidity, but the primordia of the second strain die en masse at such humidity.

Is your substrate homogeneous?

For example:

- When treated using the hydrothermal method, the bottom layer of the substrate may be waterlogged. In a tunnel, the wetter layers are often the side layers and/or the top layer if the thermal insulation of the tunnel roof is not sufficient.

In a waterlogged substrate there is free water, which during incubation collects in the layer between the film and the substrate. Microorganisms (mold or bacteria) will begin to multiply in this layer and there will be a lot of yellow wet spots or green mold in the bag.

That is, blocks made from bottom and side layers will not overgrow well. And in the substrate from the center, the mycelium grows well and gives a good harvest.

And if those blocks are inoculated with another supplier's grain spawn, you'll blame them, not your technology.

- The same situation may arise if the top bags are not completely covered with water during heat treatment of raw materials. Then part of the substrate that has undergone insufficient heat treatment may deteriorate.

These blocks will begin to rot, and you will decide that the spawn is to blame.

And your argument will be that spawn from another manufacturer is overgrown without damage.

And it won’t be a matter of spawn at all, but a difference in the properties of your substrate, even though it was processed in the same container.

The mycelium in grain can indeed be old, overpacked and of poor quality. Read my article about this.

How can you compare spawn from different suppliers?

If you are confident in the quality of your processing method, a correct comparison would be:

1. You take packages of the same strain from two or three different manufacturers.
2. You inoculate the blocks this way: inoculate a spawn packet from one supplier, then a packet from a second supplier, then again from the first, and so on. You need to sign the completed blocks immediately so as not to get confused. Or stick stickers of different colors. Write the name of the laboratory and strain on each sticker.
3.  You also need to hang or arrange blocks in the incubator in batches: part with one sticker, then with another, then again with the first...
4. Be sure to make some of the blocks in transparent polyethylene if you usually use black bags. You need to monitor the development not only visually, but also by measuring the temperature of the blocks - in the center and under the film. Be sure to record the temperature every day so you can compare the development of mycelium in the substrate.

Remember, no matter how much you want to blame the spawn suppliers for your troubles:

If the block is overgrown well, the primordia appeared on time and were beautiful at the very beginning of development, then everything that happens after is your own shortcomings in making the substrate, or shortcomings in the microclimate during incubation and in the growing room. And most often, unfortunately, it’s both.

Read more about this here.